This invention relates to transfer systems for transferring workpieces between successive die stations in a stamping press and also to a carriage component for use in such systems.
The manufacturing industry, and in particular the metal fabrication and stamping industries, commonly utilize automated systems that allow a workpiece to be conveyed or transferred between equally spaced workstations where particular operations are carried out. For example, many metal parts on automobiles and appliances are formed by means of a stamping procedure employing a series of dies that are situated on a number of aligned and equally spaced workstations within the bed of a transfer press. The part is formed progressively from a workpiece upon each stroke of the press. Automated transfer systems are typically employed to grasp the workpiece, remove it from one set of dies and then transport the workpiece laterally through the press bed to the next adjacent workstation where it will be stamped a second time with a further set of dies upon the next stroke of the press.
A press transfer system utilized in conjunction with a typical multi-stage press commonly includes at least one transversely oriented transfer rail situated adjacent to the press bed and aligned with the various workstations. Depending upon the particular application and the press layout, a single transfer rail may be positioned along one side of the press bed or, alternatively, a separate transfer rail may be located on each side of the bed of the press. Regardless, the primary function of the transfer rail is to provide a mechanism by which tools, generally referred to as grippers or fingers, may be supported adjacent to the workstations and moved to allow a workpiece to be grasped and transported to the next workstation.
Movement of workpieces from workstation to workstation involves the movement of the transfer rail in what usually amounts to a relatively complex three-dimensional manner. Described generally, this movement involves (i) moving the rail toward the workstation such that the grippers or fingers may grasp the workpiece (referred to as movement in the Y-axis direction); (ii) lifting the rail upwardly to remove the workpiece from the dies of a particular workstation (referred to as movement in the Z-axis direction); (iii) moving the rail longitudinally and parallel to the press bed to align the workpieces with the next adjacent workstation (referred to as movement in the X-axis direction; (iv) lowering the rail to allow the grippers to place the workpieces onto the next adjacent set of dies (Z-axis movement); (v) retracting the rail from the workstation (Y-axis movement) to extract the grippers from the press bed so they are not damaged with the next stroke of the press; and, finally, returning back to the starting position (X-axis movement).
The primary reason for utilizing a press transfer system in fabrication and stamping operations is to maximize production efficiency by increasing the throughput of a production line. A press and its related equipment in a stamping or fabrication facility represent a significant capital investment for a manufacturer. In order to maximize the return on that investment there is a desire to maintain presses in continuous operation and to maximize the number of workpieces moving through the press over a given length of time. As a result others have devoted a considerable amount of effort into the design of transfer rails and the mechanical, hydraulic and/or pneumatic systems that drive transfer rails in the complex three-dimensional manner described above.
Most transfer systems are limited to one direction of part flow. Prior to purchasing a transfer system, generally the manufacturer must consider which direction of part flow is required and choose the transfer system accordingly. In left-right part flow, the size of the parts that can be stamped and transferred is limited by the width (front-back) of the bed of the press or the corresponding window between press columns, whichever is smaller. Press beds are normally rectangular in shape, having their left-right width significantly greater in size than the front-back width, allowing for a greater number of progressive stations in left-right part flow, relative to front-back. In front-back part flow, the left-right width of the workstation can be significantly larger than for left-right part flow workstations which allows for parts with large blank widths (left-right) to be used. Because the bed is rectangular in shape and the front-back width is smaller than the left-right width, the number of progressive stations that can fit on the bed in this direction is limited.
In summary, if the manufacturer chooses to purchase a transfer system for left-right part flow, the maximum allowable size of the blanks to be formed will be limited by the front-back width of the press bed or corresponding column window. If the manufacturer chooses to purchase a transfer system for front-back part flow, the maximum allowable size blanks to be formed will be significantly increased with respect to maximum size in the left-right part flow direction, but the number of progressive workstations will be limited by the smaller front-back width of the press bed.
U.S. Pat. No. 4,577,748 which issued Mar. 25, 1986 to M. S. Willett, Inc. describes a transfer system that has transfer bars mounted on a frame which moves longitudinally as a unit. The bars move transversely on the frame. A drive box mounted on a side of the frame has transverse and longitudinal drive levers. The longitudinal drive lever has a roller which slides in a transverse track in one of the transfer bars to drive the frame forward and rearward and the transverse drive lever is pivotably connected to a link which is pivotably connected to a pivotably mounted crank arm. There are also carriages movable along upwardly and outwardly slanted slide assemblies mounted on the transfer bars. However, this known transfer apparatus is only designed to move the workpieces through the workstations in the left-right flow direction relative to the press.
U.S. Pat. No. 4,887,446 which issued Dec. 19, 1989 to J. H. Maher also describes a system for transferring workpieces through a series of linearly aligned workstations. The workpieces are transferred along an X-axis by a plurality of workpiece gripping fingers mounted on a transfer rail. Independently supported actuator units are provided which have a lateral arm to support the transfer rail and to impart up and down and back and forth movement to it. The transfer mechanism can be coordinated with operation of the press. However, in this known system, the individual actuator units are simply floor mounted by means of castors which permit each unit to be moved when required. Again, this transfer system is only set up for a left-right flow of the workpieces from one workstation to the next.
According to one aspect of the present invention, it is one object of the invention to provide a transfer system which employs four mounting heads that are independently movable on two support beams and that are each selectively connectible by means of a bar to another of the mounting heads for the purpose of transferring the workpieces either in a left-right flow direction or in a front-back flow direction relative to the press.
According to another aspect of the invention, it is another object of the invention to provide a transfer system that includes at least one improved mounting head horizontally movable on a horizontal support beam, this improved mounting head including a coupling for detachably connecting a mounting bar for supporting workpiece grippers, a lateral transfer mechanism for moving the coupling in a front-back direction and a vertical transfer mechanism for moving the coupling vertically.
According to yet another aspect of the invention, it is an object of the invention to provide an improved carriage apparatus for use in a transfer system, this carriage apparatus including a primary carriage body adapted for mounting on a horizontally extending support beam for substantially horizontal movement, a secondary support body mounted for vertical movement on the carriage body, and an elongate support member mounted for substantially horizontal movement on the secondary support body in a front-back direction relative to the press during use of the transfer system.